How to link libraries in cmakelists.txt

Question

I am mainly using ROS which is cmake based, where I want to link a library that I compiled previously and copied the .so and .a file to /usr/lib and .h to /usr/include.

When I compile it with gcc, there is no problem with: gcc -o test test.c -lpynq -lcma -lpthread. How can I link those libraries in the cmakelist.txt?

Thank you for the help.

EDIT: Following JohnFilleau and the answer from ChrisZZ, this is my CMakeLists.txt:

cmake_minimum_required(VERSION 3.0.2)
project(proof_of_concept_string_ips)

## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)

## Find catkin macros and libraries
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
## is used, also find other catkin packages
find_package(catkin REQUIRED COMPONENTS
  roscpp
  std_msgs
)

## System dependencies are found with CMake's conventions
# find_package(Boost REQUIRED COMPONENTS system)


## Uncomment this if the package has a setup.py. This macro ensures
## modules and global scripts declared therein get installed
## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
# catkin_python_setup()

################################################
## Declare ROS messages, services and actions ##
################################################

## To declare and build messages, services or actions from within this
## package, follow these steps:
## * Let MSG_DEP_SET be the set of packages whose message types you use in
##   your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).
## * In the file package.xml:
##   * add a build_depend tag for "message_generation"
##   * add a build_depend and a exec_depend tag for each package in MSG_DEP_SET
##   * If MSG_DEP_SET isn't empty the following dependency has been pulled in
##     but can be declared for certainty nonetheless:
##     * add a exec_depend tag for "message_runtime"
## * In this file (CMakeLists.txt):
##   * add "message_generation" and every package in MSG_DEP_SET to
##     find_package(catkin REQUIRED COMPONENTS ...)
##   * add "message_runtime" and every package in MSG_DEP_SET to
##     catkin_package(CATKIN_DEPENDS ...)
##   * uncomment the add_*_files sections below as needed
##     and list every .msg/.srv/.action file to be processed
##   * uncomment the generate_messages entry below
##   * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)

## Generate messages in the 'msg' folder
# add_message_files(
#   FILES
#   Message1.msg
#   Message2.msg
# )

## Generate services in the 'srv' folder
# add_service_files(
#   FILES
#   Service1.srv
#   Service2.srv
# )

## Generate actions in the 'action' folder
# add_action_files(
#   FILES
#   Action1.action
#   Action2.action
# )

## Generate added messages and services with any dependencies listed here
# generate_messages(
#   DEPENDENCIES
#   std_msgs
# )

################################################
## Declare ROS dynamic reconfigure parameters ##
################################################

## To declare and build dynamic reconfigure parameters within this
## package, follow these steps:
## * In the file package.xml:
##   * add a build_depend and a exec_depend tag for "dynamic_reconfigure"
## * In this file (CMakeLists.txt):
##   * add "dynamic_reconfigure" to
##     find_package(catkin REQUIRED COMPONENTS ...)
##   * uncomment the "generate_dynamic_reconfigure_options" section below
##     and list every .cfg file to be processed

## Generate dynamic reconfigure parameters in the 'cfg' folder
# generate_dynamic_reconfigure_options(
#   cfg/DynReconf1.cfg
#   cfg/DynReconf2.cfg
# )

###################################
## catkin specific configuration ##
###################################
## The catkin_package macro generates cmake config files for your package
## Declare things to be passed to dependent projects
## INCLUDE_DIRS: uncomment this if your package contains header files
## LIBRARIES: libraries you create in this project that dependent projects also need
## CATKIN_DEPENDS: catkin_packages dependent projects also need
## DEPENDS: system dependencies of this project that dependent projects also need
catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES proof_of_concept_string_ips
#  CATKIN_DEPENDS roscpp std_msgs
#  DEPENDS system_lib
)

###########
## Build ##
###########

## Specify additional locations of header files
## Your package locations should be listed before other locations
include_directories(
# include
  ${catkin_INCLUDE_DIRS}
)

## Declare a C++ library
# add_library(${PROJECT_NAME}
#   src/${PROJECT_NAME}/proof_of_concept_string_ips.cpp
# )

## Add cmake target dependencies of the library
## as an example, code may need to be generated before libraries
## either from message generation or dynamic reconfigure
# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Declare a C++ executable
## With catkin_make all packages are built within a single CMake context
## The recommended prefix ensures that target names across packages don't collide
# add_executable(${PROJECT_NAME}_node src/proof_of_concept_string_ips_node.cpp)

## Rename C++ executable without prefix
## The above recommended prefix causes long target names, the following renames the
## target back to the shorter version for ease of user use
## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"
# set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")

## Add cmake target dependencies of the executable
## same as for the library above
# add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Specify libraries to link a library or executable target against
# target_link_libraries(${PROJECT_NAME}_node
#   ${catkin_LIBRARIES}
# )

#############
## Install ##
#############

# all install targets should use catkin DESTINATION variables
# See http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html

## Mark executable scripts (Python etc.) for installation
## in contrast to setup.py, you can choose the destination
# catkin_install_python(PROGRAMS
#   scripts/my_python_script
#   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## Mark executables for installation
## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_executables.html
# install(TARGETS ${PROJECT_NAME}_node
#   RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## Mark libraries for installation
## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_libraries.html
# install(TARGETS ${PROJECT_NAME}
#   ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   RUNTIME DESTINATION ${CATKIN_GLOBAL_BIN_DESTINATION}
# )

## Mark cpp header files for installation
# install(DIRECTORY include/${PROJECT_NAME}/
#   DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION}
#   FILES_MATCHING PATTERN "*.h"
#   PATTERN ".svn" EXCLUDE
# )

## Mark other files for installation (e.g. launch and bag files, etc.)
# install(FILES
#   # myfile1
#   # myfile2
#   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}
# )

#############
## Testing ##
#############

## Add gtest based cpp test target and link libraries
# catkin_add_gtest(${PROJECT_NAME}-test test/test_proof_of_concept_string_ips.cpp)
# if(TARGET ${PROJECT_NAME}-test)
#   target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})
# endif()

## Add folders to be run by python nosetests
# catkin_add_nosetests(test)

add_executable(pc_pub_string src/pc_pub_string.cpp)
target_link_libraries(pc_pub_string ${catkin_LIBRARIES})
#add_dependencies(pc_pub_string0 proof_of_concept_string_ips_generate_messages_cpp)

add_executable(arm_to_fpga src/arm_to_fpga.cpp)
target_link_libraries(arm_to_fpga ${catkin_LIBRARIES})
# target_link_libraries(arm_to_fpga ${catkin_LIBRARIES}) /usr/lib/libpynq.so)
#add_dependencies(arm_to_fpga proof_of_concept_generate_messages_cpp)

# add_executable(pynq_test_api src/pynq_test_api.cpp)
# target_link_libraries(pynq_test_api ${catkin_LIBRARIES})

set(pynq_lib "/usr/lib/libpynq.so")
set(cma_lib "/usr/lib/libcma.so")

add_executable(pynq_test_api src/pynq_test_api.cpp)
target_link_libraries(pynq_test_api PUBLIC
  ${catkin_LIBRARIES}
  ${pynq_lib}
  ${cma_lib}
  pthread
  )
  target_include_directories(pynq_test_api PUBLIC
  "/usr/include"
)

And the error:

CMakeFiles/pynq_test_api.dir/src/pynq_test_api.cpp.o: In function `main':
pynq_test_api.cpp:(.text+0xba): undefined reference to `PYNQ_allocatedSharedMemory(shared_memory_state_struct*, unsigned int, int)'
pynq_test_api.cpp:(.text+0xc8): undefined reference to `PYNQ_allocatedSharedMemory(shared_memory_state_struct*, unsigned int, int)'
collect2: error: ld returned 1 exit status
proof_of_concept_string_ips/CMakeFiles/pynq_test_api.dir/build.make:114: recipe for target '/home/xilinx/fpga_ros_scheduler/catkin_ws/devel/lib/proof_of_concept_string_ips/pynq_test_api' failed
make[2]: *** [/home/xilinx/fpga_ros_scheduler/catkin_ws/devel/lib/proof_of_concept_string_ips/pynq_test_api] Error 1
CMakeFiles/Makefile2:449: recipe for target 'proof_of_concept_string_ips/CMakeFiles/pynq_test_api.dir/all' failed
make[1]: *** [proof_of_concept_string_ips/CMakeFiles/pynq_test_api.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

Answer 1

The quick-but-not-elegant solution:

cmake_minimum_required(VERSION 3.20) # I like newer version

project(my_project)

set(pynq_lib "/usr/lib/libpynq.a")  # the full path. if postfix is `.so`, change it
set(cma_lib "/usr/lib/libcma.a")  # the full path. change if needed.

add_executable(test_app test.c)
target_link_libraries(test_app PUBLIC
  ${pynq_lib}
  ${cma_lib}
  pthread
)
target_include_directories(test_app PUBLIC
  "/usr/include"
)

The elegant way: as JohnFilleau suggested, suppose we generate pynq and cma libraries via CMake, then we treat them as "packages", and we "find package and link package", with commands like find_package() for external installed packages, or just use target_link_libraries() if build from same CMake based project.